FI65668C - VAERMEBEHANDLINGSANORDNING FOER BEHANDLING AV SAMMANSATT MATERIAL T EX STENGRUS OCH FOERFARANDE FOER VAERMEBEHANDLING - Google Patents

Description

FIELD OF THE INVENTION for heating to an elevated heat-10 space and in which, prior to directing the sludge to the furnace, it is preheated with hot gases flowing from the furnace and an improved process for heat treatment of a solid sludge stream in which the sludge is fed through a rotary kiln. to heat the material to an elevated temperature, and in which the hot gas discharged from the furnace as waste gas is utilized to pre-heat the material to be fed to the furnace. dampen the.

In a production in which minerals are heat treated by passing them through a drum furnace at an elevated temperature, a preheater is generally used to preheat the substances inside the feed or inlet end of the drum furnace by contacting them with hot waste gases discharged from the furnace.

In the case of relatively fine, granular materials, the preheater often consists of a series of cyclone housings in which the cyclones provide a cascade of granular material in contact with the heated gases. Preheaters of this 30 general type are exemplified in am. Patent Nos. 3,738,794; 4,004,876; 4,002,568 and 4,105,396.

When the minerals to be heat-treated are in the form of a relatively coarse aggregate, a different pre-35 meni must be used. A commercially available preheater designed to handle relatively coarse material heaps operates on a batch basis and uses a device that places a static stacking layer in the hot gas stream and a massive immersion piston device regularly removes the preheated stacking layer prior to re-formation. Other types of preheaters designed to treat solid aggregates are disclosed in the aforementioned Patents Nos. 3,159,386; 3,671,027; 3,883,294 and 4,038,025.

The previously available substance-10 heap preheaters known to the applicant are relatively large and quite expensive. Preheaters usually have several moving parts that are exposed to high temperatures and temperature changes and therefore require quite a lot of maintenance. In addition, the stack preheaters known to the applicant are relatively inefficient and leave a considerable amount of usable thermal energy in the waste gases which are discharged into the open air. Due to this inefficiency and the relatively high temperature of the waste gases discharged from the preheater, it is generally necessary to use some means with the known preheaters to cool the gases after passing through the preheater and before filtering them in the hose filtration chamber. This is usually done either by using an external condenser or by taking in air from the outside, which is mixed with hot gases to lower their temperature. The former method means additional energy consumption, while the latter method increases the load on the filtration system and thus makes the filter larger and more expensive.

In view of the above, po. It is an object of the invention to provide an improved apparatus and method for preheating a substance pile in connection with a rotary kiln, which overcomes the disadvantages and limitations of previously known preheating apparatus and methods.

It is a further object of the invention to provide a preheater for a material seam 35 having a structure such that it helps to remove dust from the material, thereby reducing the load on the filter.

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Po. according to the invention, the material pile for preheating with waste gas includes directing the material pile downwardly towards the furnace along a predetermined, tortuous path, the material pile being in the form of a thin bed and the waste gas In this way, close contact of the collection of substances with the gas flow is achieved and a very efficient transfer of heat 10 is achieved between them. In addition, the sloping path of the collection and the direction of the gas flow relative to it help to remove any dust particles that may be present in the thin layer of material and the gas flow carries away the dust particles.

To deal with a collection of subjects po. In the heat treatment device according to the invention, the material seam preheater comprises two permeable retaining walls having a non-direct, tortuous shape and extending substantially vertically opposite and spaced apart to form an elongate, substantially vertical channel having a gap the material pile extends downwards in a thin layer, each opposing gas-permeable retaining wall consisting of a series of laterally and spaced apart slats joined together to form segmental wall portions arranged so that the segmental wall portions are alternately inclined on opposite sides of the vertical axis and arranged convergentially and inclined at an angle downwards in the direction of travel of the material seam and are arranged overlapping each other and that the device has means cooperating with the corresponding segment of the retaining walls with the wall portions to direct the heated gas flow from the furnace alternately through each segmental wall portion to direct the heated gas repeatedly laterally back and forth through a thin layer of material in the duct 35.

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Po. the apparatus of the invention can be effectively utilized in conjunction with a rolling furnace to preheat the material seam by allowing it to contact the hot waste gases of the furnace before the material is fed to the furnace. When used in this way, the very efficient heat transfer properties of the preheat-5 entim cause a very significant reduction in the temperature of the furnace waste gases as well as a considerable preheating of the material deposit. This reduces the overall fuel demand of the furnace and allows for more efficient production. In addition, the relatively cold gases discharged from the preheater can be immediately filtered and discharged without the need for additional cooling, which is generally necessary with previously known preheaters in the material pile.

Some features and advantages of the invention have been described above, and others will become apparent from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 shows a slightly schematic vertical sectional view of a device circuit for handling a material pile in an oven and po. a material pile preheater according to the invention, which preheats the material pile before it is fed to the furnace; Fig. 2 shows a perspective view of a preheater of the invention, the outer housing of which is shown in broken lines to show more clearly the internal structure of the preheater; Fig. 3 is a side cross-sectional view of the preheater; Fig. 4 shows a detailed perspective view of the structure of the retaining walls of the material seam inside the preheater; and Figure 5 is an enlarged, detailed cross-sectional view of a portion of the preheater.

Referring to the drawings in more detail, Figure 1 shows a device connection for treating and heating a mass of material through a drum or wort furnace. With such a device, for example, calcination of limestone or roasting of various other minerals or ores can be performed. Minerals or other substances, treated with po. device, is referred to herein as a "mass of matter," but it is clear that this designation is not limited to a mineral or stone having a particular chemical composition. The device shown is specially designed to handle a relatively coarse mass of material in the form of lumps, which can have a maximum diameter of about 50-75 mm, as opposed to fine, granular or powdery materials with a size comparable to e.g. sand. The device shown is particularly suitable for the treatment of a material seam 10, the size of which has been classified at least in part, preferably in the size range of about 19.05 to 38.1 mm.

The apparatus shown in Figure 1 includes a conveyor 10 which conveys a material pile from a non-shown feed source to a material pile at the top of the preheater 15 indicated by the general numeral 11. The material pile is slowly fed down through the preheater 11 as described below, contacting it with hot waste gases indicates general number 12. Thus, the furnace hot waste gases preheat the substance-20 pile prior to feeding the substance to furnace 12. The preheated substance pile is then fed longitudinally through the wort furnace 12 while being heated to the desired temperature and discharged from the furnace at its opposite end. 25, the structure of the cooler 13 is known and has a grate 14 on which the heated material pile is lowered, as well as a plurality of fans 15 mounted so as to direct air through the grate 14 into contact with the heated material pile. nssa this to cool. The thus cooled material pile is removed from the grate 14 and lowered onto a conveyor 16 which transports it to another storage or subsequent use.

The air passing through the material sump in the condenser 13 is heated by the material sump and is directed from the condenser 13 35 to one end of the elongate wort furnace 12. The oven more specifically includes an elongated, hollow tubular body 17 which is mounted for rotation about its longitudinal axis on suitable supporting columns 6 65668 18, and a drive motor 19 being suitably connected to the tubular body for rotating the direction of the arrow. The tubular body 17 is directed onto a gradually inclined surface, which is known so that the rotation of the tubular body 5 gradually feeds the material seam through the furnace. The furnace 12 further includes a burner 21 which burns carbon powder or other suitable fuel and which is mounted in a suitable housing 22 at the discharge end of the tubular body 17. The burner 21 directs the flame in the longitudinal direction inside the tubular body 17 to heat the material pile in the furnace 10 to the desired temperature. The heated air and the combustion gases of the burner 21 pass longitudinally through the hollow tube body 17 of the furnace in the opposite direction to the collection of material passing therethrough and flow from the opposite end 15 of the tube body to the preheater 11. Here the hot gases come into contact with the incoming material before heating. is fed to the furnace 12, while the temperature of the exhaust gases thus decreases. The gases exit the preheater 11 at its upper end and are directed 20 via a line 23 to a dust collection box 24 which separates the heavier dust and other particles from the gas stream. The gases are then passed through line 25 to a suitable filter, indicated by the general numeral 26. In the embodiment shown, the filter 26 is a hose filter chamber commonly used to remove dust and other small particles from the gas stream, and the hose filter chamber includes a plurality of elongate, tubular and bag filters. From the filter 26, the gases are directed along line 27 and through a fan 28, which provides a gas flow through the hose filter and preheater 30 and the furnace, after which the gases are removed to the outside air through a chimney 29.

The typical temperature of the gases leaving the furnace 12 is about 590-665 ° C. After passing through the preheater 11, the temperature drops to about 65.6-93.3 ° C. 35 This very significant decrease in temperature, which is po. due to the high degree of efficiency provided by the preheater of the invention, allows exhaust gases to be passed directly to the filter 26 without the need for an additional cooler or 65668 to take in air from outside to lower the gas temperature, as is required in known material accumulation heat treatment systems. By efficiently recovering the otherwise wasted heat of the exhaust gases and transferring it to the incoming material, a large amount of otherwise wasted thermal energy is saved and the fuel requirement of the burner is reduced. In addition, with this arrangement, a much higher production capacity of the furnace can be achieved, so that the treatment of the material seam takes place at a speed of mouth-10 rheumatism.

Referring now more closely to the structure of the material seam preheater 11, best shown in Figures 2 and 3, the preheater includes an elongate, hollow vertical housing 31 having a circular cross-sectional shape in the illustrated embodiment 15, as shown. The housing 31 has an inlet opening 32 near its lower end, which opening is connected to one end of the tubular body 17 of the weaning furnace 12 to receive the hot waste gases discharged by the furnace. The housing is clad with a suitable insulating material 33 which protects the housing 31 from the insulating 20 and prevents the loss of radiant heat therefrom. The housing 31 has an outlet opening 34 near its upper end, through which opening the gas flow leaves the housing 31 and is directed via a line 23 to the dust collection box 24.

Inside the housing 31 extending in its longitudinal direction 25 are two material seam retaining walls 36 which are placed close to each other so that an elongate, vertically extending channel or trough 35 for the material collection is formed between them. The elongate channel 35 of the material seam has a relatively narrow cross-section and receives the material seam 30 at its upper end and keeps it in the form of a relatively thin layer, e.g. 101.6-127 mm thick, which is guided downwards along the channel 35. As shown, the retaining walls 36 have a non-rectilinear, tortuous shape so that a thin layer of material becomes guided by the tortuous path 35 as it travels downward through its elongate, narrow channel.

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Each non-linear, tortuous retaining wall 36 consists of a series of inclined segment wall portions 37, each of which is inclined at a relatively small angle from the vertical axis. The angle of inclination of the various segment wall portions 37 is preferably in the range of about 10-25 ° from the vertical axis and more preferably about 17-18 °. The different segment wall portions, which together form each retaining wall, are arranged to tilt alternately to one side of the vertical axis and alternately to the opposite side of the vertical axis. Thus, the thin layer of material pellet becomes guided laterally back and forth in opposite directions along downwardly sloping passageways as it passes downwardly through the elongate channel 35.

Retaining walls 36 forming a material seam.

The elongate duct or chute 35 are gas permeable in structure so that hot gases in the housing 31 can flow freely through a thin layer of material. As shown, the tortuous, gas permeable retaining walls 36 are arranged in the hollow interior of the housing 31 so that hot the gases flowing inside the housing are repeatedly directed through the retention walls 36 and into contact with a thin material sauna layer interposed between the walls. More specifically, a series of barrier plates 38 extend outwardly from the retaining walls 36 to the enclosing housing at spaced apart locations in the longitudinal direction of the retaining walls to direct the gas flow upwardly along a tortuous path repeatedly laterally back and forth through the retaining walls and thus repeatedly guiding through it.

As best seen in Figure 3, the wall 41 extends between the uppermost ends of the retaining walls 36 and the surrounding housing 31, forming a funnel at the upper end of the housing that receives the feed material and the wall 41 is inclined toward the open top of the elongate channel 35 to direct the material into the channel. The elongate, cylindrical roller 42 is below the lower end of the retaining walls 36 in a blocking relationship with the lower end of the channel 9 65668 so that the material seam keeps the channel substantially filled. The roller 42 is rotatably driven by a drive motor 43 (Fig. 2) to discharge the material deposit from the lower end of the channel in a controlled and metered manner.

The rotational speed of the drive motor 43 is preferably proportional to the rotational speed of the rolling furnace such that as the speed of the furnace is increased, the speed of the roller 42 increases correspondingly so that the material accumulation is fed to the furnace faster.

Once the preheated material has been discharged from the lower end of the channel 35, it falls under its own weight through the inlet pipe 44 and inside the interior of the rolling furnace 12.

As best seen in Figures 4 and 5, the gas permeable walls 36 forming the substance passage 35 have a grille structure and consist of a plurality of rack-15 lattice and laterally extending slats 46 extending substantially the full width of the trough 35 and connected to opposite closed end walls 47. The slats 46 of each group are spaced apart so that gas can easily flow between them, and reinforcing spacers 48 are mounted between adjacent slats at spaced apart locations to provide better structural rigidity in the width of the retaining wall. As shown, the slats are inclined at an angle downwards in the direction of travel of the material stack and are arranged convergentially with the opposite group of slats. The slats of both groups overlap, which helps guide the Alne pile downward in its path, while keeping the material pile inside the elongate channel, while the gas can easily flow into and through the thin layer of material.

As noted above, the various segment wall portions 37, which together form the retaining walls 36, are oriented obliquely with respect to the vertical axis so that the advancing material column moves downwardly along an inclined, tortuous path. The upward passage of gases through the different segment wall portions is arranged so that the gases enter the thin material layer sensing the substance from the two opposite wall portions and exit the layer in the upper two segment wall portions. Thus, as indicated by the flow arrows α in Fig. 5, the slat structure of the segment wall portions provides guidance of the hot gases to the inclined, thin layer of material at an angle downward in approximately the same direction as the direction of travel of the material. The gas flow thus promotes the downward movement of the layer of material instead of interfering with or impeding the flow of the substance, as could happen if the gas flow passed through the layer of material in the other direction. By directing the air flow at an angle through the layer of material, the slat structure of the wall part 37 is further extended to extend the distance that the gas must pass through the layer, which enhances the contact and heat transfer between the gas and the material.

The inclined orientation of the segmental wall portions at an angle is also important because it provides efficient removal of dust and other fine particles from the material and prevents the air passages between the different slats 46 from being blocked by the dust accumulating between the slats. This 20 is best understood by looking again at Figure 5. As this figure shows, the material seam closest to the lower two segment wall portions 37, i.e. the wall on the inlet side where air enters the material layer, is in a relatively dense state as it carries the weight of the material 25 on top. In contrast, the material seam closest to the outflow wall, i.e. the right-hand segment wall part in Fig. 5, does not support the weight of the material on top, so it is less tight. Thus, the looser stack of material can move and turn around as it progresses down the column, and the outwardly flowing gases can easily sweep away any dust that may be carried with the material. In addition, the slats 46 of the outflow wall are oriented at an angle upwards relatively sharply, so that according to the flow arrows b in Fig. 5, the gases are directed upwards at an angle of 35 ° between the slats. The relatively steep sloping orientation of the slats helps to keep the air ducts free of accumulating dust, as the exposed surfaces of the slats tilt too sharply 11 65668 and no dust can accumulate on them and the air flow can carry any dust that may accumulate on the slats.

When dust or other particulates are removed from the material accumulation column, the heavier particles tend to separate or fall off instead of being entrained with the gas stream, and the dust or particulate matter settles on the top surface of the barrier plates 38. As shown, the barrier plates tilt downwardly from the retaining walls 36 and outwardly toward the surrounding housing 31, so that they direct dust or particle outwardly toward the housing 31. As shown in Figure 2, the inclined barrier plates 38 have a semi-oval shape because the surrounding housing has a circular shape. cross-section, so that the plates convergentially direct the collected dust or particulate matter to a common location at the lowest point of the plate. At this point, there is an opening 51 in the wall of the housing 31 through which the accumulated dust can be removed from the housing, and a line 52 is connected to the opening to take the dust away to a suitable collection point. Similar openings 51 and wires 52 are used with each barrier plate 38 in the preheater.

Due to the tortuous structure of the retaining walls 36 and the arrangement of the barrier plates 38, the hot gases from the furnace are repeatedly guided through the thin material seam layer 25 alternately from different directions, i. first on one side of the thin layer and then on the other side. Thus, the different side of the material pile is exposed to the flowing gases at different points in each case, which makes the heat transfer from the flowing gases to the material pile as large as possible.

As the gases have repeatedly passed back and forth through a thin layer of material and have reached the top of the housing 31, their temperature has dropped considerably and their heat content has shifted to the material pile. The gases thus cooled leave the housing through the outlet opening 34 and the floods 35 are directed through a line 23 to a dust collection box 24, where the gases are directed under the barrier plate 24a. Because the gases have a significantly larger flow area in the dust collection box 12 65668, their velocity decreases significantly, allowing dust and particulate matter previously introduced into the gas stream to drop out of it before being directed to the filtered 26.

The drawings and the description show the preferred embodiments of the invention and it is difficult to use certain names, this is done only to illustrate the invention and not to limit it.

Claims (3)

1. Heat treatment apparatus for treating a solid composite material, e.g. coarse stone gravel which has a drum furnace (12) through which the composite material is measured along a downward sloping path and where a heated gas is guided through the furnace (12) in an opposite direction to the direction of movement of the composite material to heat. the composite material to an elevated temperature and being the composite material before being guided into the furnace (12) preheated by the heated gases flowing from the furnace (12), characterized in that the preheater (11) of the composite material is pours two permeable barrier walls (36) of non-linear zigzag shape which extend substantially vertically in opposition, separated relative to each other to form a substantially vertical oblong channel (35) having a narrow cross-section such that the composite material moves downward in the form of a thin layer, each of the opposing gas-permeable barrier wall (36) consisting of a series of laterally separated separators (46) which are said to be mm connected to form segment wall portions (37) which are so arranged that the segment wall portions (37) incline alternately on opposite sides of the vertical axis, and the slats (46) in opposite series are arranged converging and inclined at an angle downward in the direction of movement of the composite material. and they are located in overlapping relationship to each other, and the device has means (38) which cooperate with respective segment wall portions (37) in the barrier walls (36) to control the heated gas flow from the furnace (12) in turn. through each segment wall portion (37) so as to control the heated gas repeated ginger laterally back and forth through the thin composite material layer in the channel (35). 2. A heat treatment device according to claim 1, characterized in that the inclined segment wall portions (37) start at an angle between about 10 ° and about 25 ° from the vertical axis.